In construction and architecture, a suspended ceiling (also referred to as a drop or dropped ceiling) commonly is used to provide a finished ceiling surface in a room or other architectural space. In some instances, often in pre-existing structures, a suspended ceiling may be installed at some level below an existing ceiling to conceal an older damaged ceiling and/or provide a new appearance in the architectural space in which the suspended ceiling is installed. In other applications, suspended ceilings may be installed in newly-constructed archictectural spaces, based in part on their relative ease of installation. In one noteworthy aspect, a suspended ceiling typically permits piping, wiring and ductwork to be easily and conveniently concealed in an area between a pre-existing ceiling (or other architectural framework) and the suspended ceiling itself. This area above the suspended ceiling commonly is referred to as a plenum.
FIG. 1 generally illustrates a typical suspended ceiling implementation. A conventional suspended ceiling 1000 employs a grid system 1020 (also referred to as “grid-work”) of metal channels that are suspended on wires 1100 or rods 1120 from an overhead structure (typically a pre-existing ceiling or architectural framework). The overhead structure is not explicitly shown in FIG. 1 to permit a view of the plenum 1140, or the area above the suspended ceiling 1000. The metal channels of the grid system 1020 are configured to form a regularly spaced grid (typically a 2 foot-by-2 foot or a 2 foot-by-4 foot pattern) of square or rectangular cells between the channels. The cells of the grid typically are filled with tiles or panels 1080 which drop into the grid system 1020. The tiles 1080 generally are formed of lightweight materials having a variety of finished surface textures and colors, and may be particularly designed to facilitate acoustic or thermal isolation as well as fire safety. Once installed, the tiles 1080 may be easily removed and replaced to provide access as needed to the plenum 1140 (where there may be various wiring, pipes and ductwork requiring repair or alteration).
As indicated in FIG. 1, the grid system 1020 generally includes multiple main channels 1040, which are supported by the suspension wires 1100 (or one or more rods 1120) attached to the overhead structure. The grid system also includes a plurality of cross channels 1060, which may be connected in an interlocking fashion to the suspended main channels. As illustrated in FIGS. 2(a), 2(b), and 2(c), the main channels and the cross channels of the grid system 1020 generally are in the shape of an upside-down “T”, wherein a bottom portion 1360 of the upside-down “T” forms a set of flanges, i.e., one flange on either side of a center rib 1340 of the channel, which supports adjacent ceiling tiles 1080 resting in the grid system 1020. Various tile edge-profiles are possible such that the bottom portion 1360 of a channel may be fully or partially exposed, or completely hidden; for example, FIG. 2(a) illustrates a first tile configuration (essentially square edges) resulting in an exposed bottom portion 1360 of a channel, FIG. 2(b) illustrates a second tile configuration (bevelled edges) resulting in a recessed bottom portion 1360 of a channel, and FIG. 2(c) illustrates a third tile configuration (slotted edges) resulting in a hidden bottom portion 1360 of a channel, in which the flanges formed by the bottom portion of the channel are inserted into the slotted edges of the tiles.
FIGS. 3(a) and 3(b) illustrate the interlocking process of a cross channel 1060 and a main channel 1040 of the grid system 1020 shown in FIG. 1. Each main channel 1040 includes multiple slots 1300 punched periodically along the channel (e.g., every 12 inches) to provide for the attachment of cross channels 1060. Each cross channel 1060 includes end tabs 1320 that are pushed into and interlock with the slots 1300 along the main channels.
As also illustrated in FIG. 1, one or more of the cells formed by the grid system 1020 may be occupied by a lighting fixture 1200, which rests in the grid system 1020 in a manner similar to that of the tiles 1080. While the tiles 1080 are appreciably lightweight, the more substantial weight of the lighting fixture 1200 generally requires that the lighting fixture is itself suspended by wires 1100 or otherwise coupled to and supported by an overhead structure, so that it does not rely exclusively on the grid system 1020 for support. Various types of fluorescent and incandescent lighting fixtures having dimensions similar to those of the tiles 1080 are conventionally employed in suspended ceilings as substitutes for one or more tiles 1080. With reference again to FIG. 2(a), such lighting fixtures are generally configured to rest on top of the flanges formed by the bottom portion 1360 of the main and cross channels of the grid system 1020. Other types of conventional lighting fixtures (e.g., incandescent, fluorescent, halogen) are designed to be recessed into a hole cut into a tile 1080, such that the lighting fixture does not completely occupy a cell formed by the grid system, but merely occupies a portion of the cell area together with a remaining portion of the tile into which the fixture is recessed.